Usually due to renal failure. Causes arrhythmia and death…

Treatment

• Slow injection of calcium – note calcium chloride and gluconate both available so potential for confusion. Dose is 0.11 mmol/kg, to be given over 5–10 minutes, maximum 4.5 mmol (0.11 mmol/kg is equivalent to 0.5 mL/kg of calcium gluconate 10%). Repeat as necessary if ECG changes do not improve.
• Bicarbonate indicated if hyperkalaemia due to acidosis or renal failure. 
• Insulin/dextrose – 10ml/kg 10% dextrose (so 5x usual dose for hypoglycaemia!), plus 0.1u/kg insulin (max 10 units), give over 5 mins. Likely peak action at 30 mins.
• Dialysis.
• Hydrocortisone if suspected Addisons. 
• ECG monitoring
• Repeated salbutamol nebs

Frusemide and calcium resonium only for asymptomatic!